Chelsea manager Carlo Ancelotti admitted his side under-achieved at Wigan, where their 100% record came to an unexpected end.
Goals from Titus Bramble, Hugo Rodallega (penalty) and Paul Scharner stunned Chelsea, who have been overtaken by Manchester United at the top of the table. Didier Drogba cancelled out Bramble's opener but goalkeeper Petr Cech's red card, for tripping Rodallega which led to the spot-kick in the 53rd minute changed the face of the game at the DW Stadium.
Ancelotti said: "We did not play a good game - it was a bad performance. I do not know why we did not play well. But these things can happen after a lot of victories. We have to accept this loss and fix things for our next match."
He added: "Wigan played better than us. They were well organised and played good football. I was surprised. This was the right result.
"We played well in the first 10 minutes but when we lost the first goal it became more complicated.
"We started the second half better, then there was the penalty. I do not want to comment on it. I know Cech was unhappy but that is normal in that situation."
Scharner scored Wigan's third goal in stoppage-time form close range when Chelsea were down to nine men, with Ashley Cole going off with a knee injury.
Midfielder John Obi Mikel had earlier suffered an ankle problem and did not appear for the second half.
Ancelotti added: "It was impossible at the end of the match with nine against 11 when Ashley was injured. We are disappointed at what happened in this game. I did not rate this performance but in football you have to look forward.
"We might not be top of the table now but there will be a lot of competition and change until the end of the season."
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